Filter choke for high electrical voltages and large outputs

ABSTRACT

A filter choke is formed of a magnetically unshielded winding, a step selector switch electrically connected to the winding and a load selector switch electrically connected to the step selector switch. The two switches are disposed side-by-side in a tank which includes a top closure provided with an opening vertically above the step selector switch. The winding is secured externally to the closure above the opening and is surrounded by a bushing insulator made of an electrically insulating material. The bushing insulator is supported by the closure and is in axial alignment with the closure opening.

United States Patent 11 1 Linnert et al.

[ FILTER CHOKE FOR HIGH ELECTRICAL VOLTAGES AND LARGE OUTPUTS [75] Inventors: Hans Linnert, Post Wintersdorf;

Walter Muller, Schwabach; Georg Weigel, Nurnberg, all of Germany [73] Assignee: Transformatoren Union Aktiengesellschaft, Stuttgart-Bad Cannstatt, Germany [22] Filed: Apr. 5, 1973 [21] App]. No.: 348,090

[30] Foreign Application Priority Data Apr. 5, 1972 1 Germany 2216325 [52] US. Cl 336/58, 317/l57.6, 336/94,

[51] Int. Cl. H0lf 27/02 [58] Field of Search 336/58, 90, 92, 94, 105, 336/150; 3l7/l57.6; 323/435 [56] References Cited UNITED STATES PATENTS 1,859,969 5/1932 .lansson 3l7/l57.6

I 1.111 3,818,400 June 18, 1974 2,294,712 9/1942 Bolte 336/94 2,668,274 2/1954 Schneider 336/94 x 3.175.148 3/1965 Swoish et al 336/94 x Primary ExaminerThomas J. Kozma Attorney, Agent, or Firm-Spencer & Kaye 57 ABSTRACT A filter choke is formed of a magnetically unshielded winding, a step selector switch electrically connected I to the winding and a load selector switch electrically connected to the step selector switch. The two switches aredisposed side-by-side in a tank which includes a top closure provided with an opening vertically above the step selector switch. The winding is secured externally to the closure above the opening and is surrounded by a bushing insulator made of an electrically insulating material. The bushing insulator is supported by the closure and is in axial alignment with the closure opening.

11 Claims, 2 Drawing Figures FILTER CHOKE FOR HIGH ELECTRICAL VOLTAGES AND LARGE OUTPUTS BACKGROUND OF THE INVENTION grounded tank to pass the test with the full test voltage and, on the other hand, the tank and other adjacent metallic components have to be shielded from the magnetic field of the windings by means of a screen which is disposed between these components and the winding and which is made of laminated transformer iron in order to maintain the additional losses at the lowest possible value.

In case winding arrangements of the aforeoutlined type are used as choking coils in filter chokes to eliminate harmonic voltage and current oscillations that are higher than the line frequency, a near perfect linear characteristic is required. For this reason, the screen made of transformer iron must not be magnetically utilized up to its saturation point. Because of this requirement, there is obtained a relatively low permissible induction for the shielding screen. Consequently, the manufacture of such screens requires substantial expense with regard to material and labor if the desidera-' turn for a linear characteristic for the filter choke is to be met.

SUMMARY OF THE INVENTION It is an object of the invention to provide an improved filter choke of linear characteristic which -is economical to manufacture and in which the overall dimensions are maintained at the smallest possible value.

This object and others to become apparent as the specification progresses are accomplished by the invention, according to which, briefly stated, a load selector switch and a step selector switch are mounted side-byside in a tank which is closed by a top closure. There is further provided a bushing insulator made of a solid insulating material and arranged above the step selector on the closure. The bushing insulator surrounds the magnetically unshielded winding of the filter choke. The inner spaces enclosed by the tank and by the bushing insulator are connected to one another by means of an opening which is provided in the closure and which is coaxial with the bushing insulator.

The filter choke arrangement according to the invention is very advantageous in that both a magnetic shielding and a main electrical insulation for the winding may be omitted. In addition, a voltage control is accomplished along the surface of the bushing insulator which, in conventional devices, could be accomplished only by means of a complex controlled duct, such as a condensator duct.

It is a further advantage of the invention that instead of the single-column structure of the stepping switch that is conventional in transformer designs the stepping switch according to the invention is divided into sideby-side disposed two structural groups, that is, a load selector switch and a step selector switch so that by virtue of the reduced overall structural height of the filter choke the high-voltage duct may remain in place on the tank even during shipment of the device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side elevational sectional view of a preferred embodiment of the invention.

FIG. 2 is a plan view of the same embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the figures, in a flat (relatively shallow) tank 4 having an oval base 8 and an oval top clo sure 9 there are mounted at opposite ends, above and spaced from the base 8, a step selector switch 5 and a load selector switch 6 in a side-by-side relationship.

The axes of the step selector switch 5 and the load selector switch 6 are parallel to one another and normal to the base 8.

In the closure 9 vertically above the step selector switch 5 and in axial alignment therewith there is provided an opening 9a. On the closure 9 externally of the tank 4 and in axial alignment with the opening 9a there is disposed a bushing insulator or insulating hood 2 which is made preferably of porcelain. A coreless winding 1 designed as a tubular winding and made of disc coils is arranged concentrically with respect to the bushing insulator '9 and is disposed on insulating rings 10 above the opening 9a of the closure 9. As may be observed from the figures, the axially aligned winding 1, bushing insulator 2 and step selector switch 5 are situated at one end of the tank 4. On the bushing insulator 2 there is provided an external terminal post 3 which is electrically connected with the upper terminals of the winding 1 and to which there is coupled an external high-voltage line (not shown). The electric conductors 10a required for an electrical connection between the step selector switch 5 and the winding 1 pass through the opening 9a.

The inner spaces enclosed by the tank 4 and the bushing insulator 2 are completely filled with a cooling and insulating liquid, such as transformer oil which, as it heats up during operation, is withdrawn from the upper part of the bushing insulator 2 through a conduit 7 that projects upwardly beyond the winding 1 and a suction conduit 12. The conduit 7 is made of a nonmagnetic insulating material; Subsequent to cooling, the oil is reintroduced into the tank 4 through a coupling nipple 11 (FIG. 2).

Adjacent the bushing insulator 2, at the other end of the tank 4 above the load selector switch 6 and an opening 9b provided in the closure 9, thereis provided a gas dome 13 which receives the gases generated during switching for preventing these gases from penetrating into the space surrounding the winding 1. To the outer wall face of the tank 4 adjacent the load selector switch 6 there is secured a stepping switch-operating device 14 which is mechanically connected to the load selector switch 6 and the step selector switch 5 as symbolically indicated by the dash-dot line 14a. The lateral tank wall further supports a low voltage terminal 15.

Due to the disc coils of which the winding 1 is formed, the high voltage is practically linearly decreasing from the top downwardly within the bushing insulator 2.

throu h the lEW NiSJQPPPElfEQQlEll o dcu r t conductor of the load selector switch 6 through the low-voltage terminal 15 connected to Qe loa d selector switch by a conductor 10c.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

We claim:

1. in a filter choke having a linear characteristic and used for high electrical voltages and outputs, the improvement comprising in combination:

a. a tank having a top closure;

b. a magnetically unshielded winding secured to said closure and disposed externally of said tank;

c. a bushing insulator of electrically insulating material mounted on said closure and surrounding said winding;

' d. a step selector switch electrically connected to said winding and disposed in said tank vertically below said bushing insulator e. a load selector switch electrically connected to said step selector switch and disposed in said tank in a side-by-side relationship with said step selector switch; and

f. means defining an opening in said closure, said opening being axially aligned with said bushing insulator and maintaining communication between the spaces enclosed by said tank and by said bushing insulator.

2. A filter choke as defined in claim 1, wherein said tank has an oval base and said top closure is'of oval configuration.

3. A filter choke as defined in claim 1, wherein said bushing insulator, said step selector switch and said 4 opening are disposed in an axially aligned relationship at one end of said tank.

4. A filter choke as defined in claim 3, including electric conductors connecting said winding with said step selector switch, said conductors pass through said opening.

5. A filter choke as defined in claim 1, wherein said step selector switch is disposed at one end of said tank, the improvement further including a switch-operating device secured externally to another, opposite end of said tank, said switch-operating device is operatively connected with said load selector switch and said step selector switch.

6. A filter choke as defined in claim 1, including means defining an opening in said closure vertically above said load selector switch, a gas dome mounted on said closure vertically above said load selector switch for receiving the gases generated during the operation of said load selector switch.

7. A filter choke as defined in claim 1, wherein said winding is a tube-shaped winding formed of disc coils.

8. A filter choke as defined in claim 1, further comprising means for filling with insulating liquid the spaces enclosed by said tank and said bushing insulator and a conduit of non-magnetic insulating material for carrying said insulating liquid, said conduit passes axially through said winding and projects upwardly therebeyond.

9. A filter choke as defined in claim 1, said winding having an upper end and a lower end, the improvement further comprising a high-voltage terminal post secured to said bushing insulator and electrically connected to the upper end of said winding.

10. A filter choke as defined in claim 1, said winding having an upper end and a lower end, the improvement further comprising a stepped winding constituting said lower end, said stepped winding having taps electrically connected to said step selector switch.

11. A filter choke as defined in claim 1, wherein said tank has a fiat configuration. 

1. In a filter choke having a linear characteristic and used for high electrical voltages and outputs, the improvement comprising in combination: a. a tank having a top closure; b. a magnetically unshielded winding secured to said closure and disposed externally of said tank; c. a bushing insulator of electrically insulating material mounted on said closure and surrounding said winding; d. a step selector switch electrically connected to said winding and disposed in said tank vertically below said bushing insulator e. a load selector switch electrically connected to said step selector switch and disposed in said tank in a side-by-side relationship with said step selector switch; and f. means defining an opening in said closure, said opening being axially aligned with said bushing insulator and maintaining communication between the spaces enclosed by said tank and by said bushing insulator.
 2. A filter choke as defined in claim 1, wherein said tank has an oval base and said top closure is of oval configuration.
 3. A filter choke as defined in claim 1, wherein said bushing insulator, said step selector switch and said opening are disposed in an axially aligned relationship at one end of said tank.
 4. A filter choke as defined in claim 3, including electric conductors connecting said winding with said step selector switch, said conductors pass through said opening.
 5. A filter choke as defined in claim 1, wherein said step selector switch is disposed at one end of said tank, the improvement further including a switch-operating device secured externally to another, opposite end of said tank, said switch-operating device is operatively connected with said load selector switch and said step selector switch.
 6. A filter choke as defined in claim 1, including means defining an opening in said closure vertically above said load selector switch, a gas dome mounted on said closure vertically above said load selector switch for receiving the gases generated during the operation of said load selector switch.
 7. A filter choke as defined in claim 1, wherein said winding is a tube-shaped winding formed of disc coils.
 8. A filter choke as defined in claim 1, further comprising means for filling with insulating liquid the spaces enclosed by said tank and said bushing insulator and a conduit of non-magnetic insulating material for carrying said insulating liquid, said conduit passes axially through said winding and projects upwardly therebeyond.
 9. A filter choke as defined in claim 1, said winding having an upper end and a lower end, the improvement further comprising a high-voltage terminal post secured to said bushing insulator and electrically connected to the upper end of said winding.
 10. A filter choke as defined in claim 1, said winding having an upper end and a lower end, the improvement further comprising a stepped winding constituting said lower end, said stepped winding having taps electrically connected to said step selector switch.
 11. A filter choke as defined in claim 1, wherein said tank has a flat configuration. 